Meosis Notes

7/26/2019 Meosis Notes

1/20

meiosis

Sunday, October 11, 2015

10:18 PM

Sexual reproduction

Sexual or asexual

Sexual reproduction

2 parents of opposite sex

Combination of enes from bot! parents

"!ere miosis comes in

#o come in

$ormation of ametes % come in to form &yote and !a'e ne( indi'idual

)sexual %

*n'ol'es sinle parent

O+sprin produced by mitosis % identical to parent

Many species do bot!

Some species ust do asexual

Some do asexual some of time and sexual at ot!er times

*n !ydra % oranism % celentarate

Cell % budd o+ of main body and form brand ne( little !ydra

-eetati'e % 'ery common in plants


2/20

Send out runners % ne( plantlet

.o( an o+sprin % enetically identical to main plant

)nd se'ered and o+sprin free li'in

)lready tal/ed about mitosis

Miosis % sexual reproduction

Meiosis % in'ol'ed in sexual reproduction

Produces amete cells in'ol'ed in sexual reproduction

amete cells % !aploid % !alf amount of c!romosomes

aploid made in particular part of pody called erm cells

erm cells found in particular parts of body suc! as onands % testies and o'eries ofanimals

)nd in plants

*n !umanes % ametes made in testies

Called sperm and rest of structures % deli'ery system to et sperm to e %structures do ot!er t!ins as (ell

*n female % es produced in o'aries

)nd ettin sperm to es and &yote ettin formed % place (!ere to ro(

amete producin structures in plants

$lo(erin plants

Structures produce amets

o'ary at base of 3o(er


3/20

O'ary % contains o'ules

4ui'alent of es in animal

Particular plant

Separate structure % ma/e male amets

)nt!er 6(!ere sperm oriinate7

Pollon eui'alent to animal sperm

Meiosis o'er'ie(

Main ob of meiosis % produce !aploid cells

alf number of c!romosomes as oriinal cell

.ot randomly c!osen !alf of c!romosomes

4ac! amete % one representati'e of eac! !omoloous of eac! c!romosomes

*n red to emp!asise importants

4ac! amete !as one representati'e of eac! !omoloous pair of c!romosomes

4xtra set at end % determines male or female

4ac! !omoloous pair

2 pairs of !omoloous c!romosomes

Pair number 1

4ac! x y structure

amete 1 of t!ose t(o

9oesnt matter (!ic! one

;ut one and only one

Pair number 2 % one of t!ose structures


4/20

Same for all of t!em

eneral purpose of meiosis % amete cell t!at !as !alf of oriinal cell

alf of oriinal cell

Maintain a constant amount of enetic information

*f (e didnt do meiosis

Produced t!ins (e call ametes by mitosis

amete cell from one parent to anot!er parent

C!romosome % double

4ac! eneration double until cell c!o/ed (it! c!romosome


5/20

>i/e mitosis except

#!ere are 2 cell di'isions

Meiosis 1 and meiosis ii

)nd !omoloous c!romosoems are separated

.atural (orld %

Meiosis % more li/e mitosis (it! extra t!ins

$irst t!in

C!romosomes duplicated

.ot ma/e lot of sence

"!y duplicate (!en oal is to cut in !alf

)s (ell see (it! e'olutionary /inds of t!ins

.ot al(ays most e?cient

;ut e'olution ta/es preexistin systems and modi@es to produce ne( /inds oft!ins

Meiosis % t!ins !appenin li/e mitosis % some c!anes

1 9uplicatin c!romosomes2 omoloues pair up 6synapsis 7 Meisis 1 % metap!ase % ri!t up next to eac! ot!er % one oes to one side one

oes to t!e ot!er % separate ot!ersA Separate c!romatids 6meiosis **7 % still !a'e c!romosomes in duplicated

condition % separate t!em

#(oB 9uplicate c!romosomes

Cell di'ision 1 % do is separate !omoloues % still left (it! c!romosomes induplicated condition

)not!er meiosis to separate sister c!romatids


6/20

s!aped structure

#(o !omolous c!romosomes

s!aped on top in li!t blue

One !omoloous already duplicated

Dnderneat! it ot!er !omoloue t!at oes (it! it, also duplicated

#(o e'ents of miosis

)lready duplicated and !omoloous pairin up and comin toet!er

.ext e'ent

Separate from eac! ot!er

#(o !omoloous c!romosomes

Separated

Meiosis 2

One !omoloous c!romosomes

Still duplicated condition

a'e to separate sister c!romatids


7/20

Separate sister c!romatids

4'ent ta/es place in second cell di'ision miosis 2

Meiosis 1

same p!ases as mitosis

Prop!ase % uniue t!in % !omoloous c!romosomes pair up

Pair li/e t!at synapsis comin toet!er

Metap!ase % pairs of !omoloues line up on euator

)nap!ase and telop!ase

omoloous c!romosomes mo'e to opposite poles

"!ic! !omoloue ends up at (!ic! pole is random

>ine up at euator

Sometimes mot!er on left side

Sometimes mot!er on ri!t side

Eandom

omoloues separate

*n anap!ase and telop!ase

et all !omoloues from fat!er oin one side and from mot!er oin to oneside

Eandom mix of t(o

Montra !olds

4ac! of ne( cells only !a'e one representati'e from !eac! !omoloous pair


8/20

One t!in see !appenin

omoloous pairs linin up next to eac! ot!er

9o more t!an t!is

Crossin o'er t!at !appens (!en t!ey line up next to eac! ot!er

Synapsis

Metap!ase % meiosis 1

Pairs lined up toet!er on euator of cell

*n box % 1 !omoloue and bottom you see ot!er !omoloue

*n anap!ase and telop!ase

C!romosomes separated

#elop!ase % top portion of cell % one representati'e from one !omoloous pair

Eesults so far

Meiosis 1

2 cells % eac! represantati'e of eac! !omoloous pair


9/20

;ut c!romosomes still duplicated state

One more cell di'ision to separate duplicated to sister c!romatids

Metap!ase

4ac! c!romosome is attac!ed at t!e euator

)nap!ase and telop!ase

Sister c!romatid separate

C!romosomes already duplicated

4nd of meiosis 1

2 cells

*n beinnin 2 cells

One representati'e

One pair of c!romosomes

$airly lare


10/20

One on ri!t

)not!er pair % /inda small side

4ac! cells !a'e one bi and one smaller c!romosome

4ac! cells !a'e to undero anot!er cell di'ision

$ocus on eit!er one of !ese

Cell on top % cell oes t!rou! metap!ase

#(o c!romosomes line up on euator of cell

)nap!ase and telop!ase % separated into sister c!romatids

Meiosis ii

Eesults % A cells % eac! (it! t!e !aploid number of c!romosomes

4ac! amete !as one representati'e of eac! !omoloous pair

Ot!er aspects of meiosis

Male and female animals % di+er a little bit

Male amete formation % A sperm % oriinal and et A sperm

4 formation same (ould be true % A e cells

et A cells but one becomes e

ot!er cells produced are called polar bodies

.ot functional ametes

"!y t!at s!ould be case


11/20

Sinle cell % underoes @rst biotic de'ision

Producin 2 cells and 2 cells producin A cells % A sperm cells

4 formation

Sinle cell

;ecomes t(o cells

)nd eac! becomes t(o cells


12/20

Only one becomes e or o'um

Eemainin % dont act as ametes at all

Eeason (!y t!ree of t!ese are t!ro(n a(ay and not used

One of t!ins you s!ould be t!in/in of

4 compared to sperm % 'ery lare

*mportant for an e to !a'e a lot of material inside it

Pro'idin nutrition for de'elopin embryo

9iaram % cyto/enisis

9i'ides contents of cell % uneual in e formation

$irst di'ision (e et

Cell on top % a lot smaller t!an cell on bottom

*n next di'ision

Still discrepency

One larer t!an ot!er

Consolidatin all cytoplasmic material and in one iant cell and muc! smallercells discarded


13/20

Dltimate purpose % ametes (it! enetic 'ariability

See !o( t!is can !appen

One t!ins t!at occurs

*ndependent assortment

Cell at top of diaram

Cell t!at !as F c!romosomes

pairs of !omoloous c!romosomes

One pair seem to be larest

One to left see smallest ri!t see someti!n in middle

pairs


14/20

omoloous pairs come toet!er

>ine up on euator

)nd (ill mo'e to opposite poles of cell

ere (e color code c!romosomes

#o /eep trac/ of t!em

9ar/ blue on bottom % from fat!er

>i!ter blue % from mot!er

Mot!er c!romosome on top

)nd fat!er on bottom

One possible con@uration

)nd it does occur

ametes

One representati'e

One bi, one small, and one medium

#(o ametes produce

One (ill !a'e all mom

)nd ot!er (ill !a'e all dad

;ut (!en !omoloous c!romosomes come toet!er

>ots of ot!er posiblities too

.ext cell s!o(s anot!er one

One of dad on top and t(o of moms

i'e us di+erent ametes

amete one !a'e small c!romosome from fat!er and lare and medium fromfat!er and complementary opposite

ametes di+erent t!an oens abo'e


15/20

enes on mot!er are di+erent t!an fat!er c!romosome

.ot completely di+erent

;ut !a'in 'ariation

Mot!er and fat!er bot! !a'e enes for eye color

Mot!er may !a'e blue eyes and fat!er may !a'e bro(n eyes

ametes 'ery di+erent from eac! ot!er

Same enes but alials may be di+erent

*ndependent assortment

One representati'e of eac! pair of !omoloues c!osen at random

Possible combinations

F c!romosomes pairs 2 to po(er G 8

umans 2 pairs 2 to 2 po(er 8 million res!uHes enetic material

8 di+erent possible ametes t!at come out of t!at

8 di+erent combinations

umans % 2 pairs

"ay to @ure out

2 to 2rd po(er

8 million di+erent combinations of mom and dad c!romosomes in ametes of!uman beins

) lot of enetic 'ariation

Ees!uHes

Ees!uHe enetic material

-ery important (!en (e tal/ about e'oltuion

4'olution % 'ariation


16/20

#al/ about t!at %

#!is diaram on left

Pair of !omolous c!romosomes % dar/ blue and li!ter blue

Prop!ase %

Pair up toet!er in synapsis

*nterestin ioned toet!er

4xc!ane c!romosonal material

Crossin o'er

Called because in second picture

9ar/ blue % arm % dar/ to li!t

Crossin o'er toet!er

$ormation /yasmada

Cross eac! ot!er

"!at !appens

>ast t(o pictures


17/20

4xc!ane of enetic information

)rm of li!t blue % attac!ed to dar/ blue and arm of dar/ blue attac!ed to li!tblue c!romosome

)t end % (e !a'e a c!romosome

More speci@cally c!romatid

Picture on left % portion of c!romosome of dar/ and li!t blue

C!romosome to ri!t

C!romatid % portion li!t blue and portion t!as dar/ blue

omoloous one from fat!er and one from mot!er

)ll c!romosome information s!uHed furt!er

$at!er oined (it! mot!er recirpical cross oin (it! mot!er

Crossin o'er

Occurs (!ile !omoloues are in synapsis

4ui'alent portions are exc!aned

Eesults in ne( enetic combinations

$urt!er s!uHin enetic material

.e( enetic combination

) lot due to independent

)nd no( youo et e'en more

enetic combination di+erent

9i+erent combinations of enetic 'arience put toet!er in di+erent (ays


18/20

;efore % independent assortment 8 million combinations

.o( because of corssin o'er

.umber of combinations of dad and mom c!romosomal material is almostin@nite

enetic 'ariability and sexual reproduction

"!y are o+sprin from sexual reproduction di+erent from eac! ot!er

;ecause of

*ndependent assortment 6eac! amete ets a random representati'e of eac!!omoloous pair of c!romosomes7

Crossin o'er

Eandom pairin of ametes from mom 6e7 and dad 6sperm7 at fertili&ation

Pool of ametes by dad and mom

Put t(o toet!er form indi'idual

C!ances of reac!in into sperm pool and e pool and by c!ance % t(oametes same

*dentical t(in

.ot part of t(innin process

Odds are 0

So many possible combinations

Only (ay % sinle fertali&ed e % oes initial clea'ae and t!ose cells o on to

ma/e indi'iduals

Meiosis summery


19/20

ametes

4ac! c!romosome duplicated durin interp!ase

;ein (it! duplicated c!romosome

#a/e loo/ at picture

>eft erm cell form male

Ei!t erm cell from female

4ac! cells !a'e one pair of !omoloous c!romosome

Simple cell

4ac! c!romosome duplicated

$ollo( one of t!ese meiosis processes

One on left

#(o x s!aped structures


20/20

9uplicated condition

Miosis 1

#(o !omoloous pair up on euator of cell and oin to separate at end ofmeisis one 2 cells eac! !as one representati'e of !omoloous c!romosomes

#a/e t!ose cells

Contain duplicate state

Sister c!romatids separated

et t(o ne( cells

4ac! !as one sister c!romatid

A amete cells

4ac! !as one c!romosone

#op of diaram % oriinal cell 2 c!romosomes

One amete formed by mot!er and one formed by fat!er

)nd put t!em toet!er fertali&ed cell called &yote

9iploid number restored at fertili&ation

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Meosis Notes